This invention relates generally to an evacuation device and especially to an evacuation device for removing volatile components from a reaction vessel of a protein sequenator.
Known evacuation devices for the reaction vessel of a protein sequenator have been characterized by first evacuation path including a first long and extremely narrow evacuation line acting as a throttle and including a shutoff valve. The first evacuation line discharges into a second evacuation line of wider cross-section also including a shutoff valve, the second vacuum path in turn discharging into a vacuum tank. The vacuum tank is evacuated by a first pump and is utilized as a vacuum reservoir for: producing suction in the reaction vessel over the first evacuation path; effecting evacuation of a fraction collector; and providing vacuum control for the pilot valves which valves open the actual dosing valves of a dosing device by pneumatic control of a diaphragm.
A second evacuation path having a larger cross-section is evacuated by a second vacuum pump and is sealed closed by an oil-sealed vacuum valve. Accordingly, over the first evacuation line, a first prevacuum builds up comparatively slowly, so that the skin of a substance contained in the reaction vessel and still in liquid form is not damaged by an extremely abrupt vacuum action thereon. Once the first prevacuum in the first evacuation line is effected, such line is closed to thereby apply the prevacuum over the second evacuation line. Thereafter, the second evacuation path is opened and utilized for generating a fine vacuum. Such a sequence of operation is required in order to separate the more vigorous vacuum functions from the less vigorous vacuum functions since otherwise the end vacuum is not sufficient to effect satisfactory drying of the film of the substance, particularly in the relatively short periods required to limit the program sequence of the reaction cycle.
It is noted that the reaction cycle in the reaction vessel cannot be effected unless two vacuum pumps are utilized. Additionally, solvent vapors drawn off by the suction from the evacuation device are directed to the vacuum pumps, causing same to settle and/or react with the oil that is needed for operating the pumps, thereby causing a rapid decline in the output and necessitating constant maintenance. Additionally it further renders it difficult to insure that identical conditions are maintained during successive reaction cycles. Moreover, the rapidly declining output of the pumps and the variable conditions during successive reaction cycles such as for example when the fraction collector has just been evacuated renders the prevacuum through the first evacuation line incapable of functioning within the time alloted for under the program, hence resulting in the substance film not being dried gently on the surface and deterioration of the substance film when the prevacuum is abruptly switched to the second evacuation line.
Still further problems occur because the substance deposits in the first evacuation path remain therein from cycle to cycle since the fine vacuum is incapable of eliminating same. Additionally the substance and solvent vapors remain deposited in large quantities in the vacuum tank thereby weakening the existing vacuum causing the results noted above as well as the improper control of the dosing valves by the pilot valves since pilot valves are operated in response to the strength of the vacuum measured thereby. Finally, if the diaphragm is damaged in any way, even a hairline crack, the active vapors will get into the pilot valves, thereby causing a disintegration of the rubber packing, such as by heptafluoride butyric acid and butane chloride, thereby diminishing the dosing in the reaction vessel hence causing heavy impurities to find their way into the reaction vessel.